1. Field of the Invention
The present invention relates to a production apparatus and a production process for a color filter, by which inks are applied to a transparent substrate using an ink-jet recording system to produce a color filter, and a liquid crystal display device using the color filter produced by this production process.
2. Related Background Art
An ink-jet recording system has heretofore been used as a recording method for printers as output means of information processing systems, for example, output terminals of copying machines, facsimiles, electronic typewriters, word processors, work stations, etc., or handy or portable printers which are installed in personal computers, host computers, optical disk devices, video devices, etc.
The ink-jet system is a system that an ink is applied to a portion to be colored from nozzles (also referred to as ejection orifices) to make a record of characters, images and/or the like, and has outstanding merits as a means for outputting high-definition images and conducting recording at high speed. A recording apparatus (ink-jet recording apparatus) using this method is an apparatus of the non-impact type and has such features that it causes little noise, color images can be formed with ease by using many inks of different colors, and the miniaturization of the body thereof and the provision of high-density images can also be achieved with ease, and has hence been being rapidly spread in recent years.
With the advancement of personal computers, particularly, portable personal computers in recent years, the demand for liquid crystal display devices, particularly, color liquid crystal display devices tends to increase. It is however necessary to reduce the cost of the color liquid crystal display devices for further spreading them. There is an increasing demand for reduction in the cost of color filters particularly given much weight from the viewpoint of the cost. Various methods have heretofore been attempted for meeting the above demand while satisfying properties required of the color filters. However, no method satisfying all the required properties is yet established. The individual methods will hereinafter be described.
A first method is a dyeing process. In the dyeing process, a water-soluble polymeric material, which is a material to be dyed, is applied to a glass substrate, and the coating film thus formed is patterned in the desired form by a photolithographic process. Thereafter, the substrate on which the coating film has been patterned is immersed in a dye bath to obtain a colored pattern. This process is repeatedly performed three times to produce a color filter layer composed of colored patterns of red (R), green (G) and blue (B).
A second method is a pigment dispersing process which has been oftenest used in recent years. In this process, a layer of a photosensitive resin, in which a pigment has been dispersed, is formed on a substrate and then subjected to patterning, thereby obtaining a pattern of a single color. This process is repeatedly performed three times, thereby producing a color filter layer composed of colored patterns of R, G and B.
As a third method, there is an electrodeposition process. In this process, a transparent electrode is patterned on a substrate. The substrate is then immersed in an electrodeposition coating fluid containing a pigment, a resin, an electrolytic solution and the like to electrically deposit a first color. This process is repeatedly performed three times, thereby forming colored patterns of R, G and B. Finally, the resin portions are thermoset, thereby forming a color filter layer.
A fourth method is a printing process in which pigments are separately dispersed in a thermosetting resin, the resultant thermosetting resin dispersions of R, G and B colors are separately applied to a substrate by repeating printing three times, and the resin portions are then thermally cured to form a color filter layer.
It is common to form a protective layer on the colored layer in each process.
The need of repeating the same process three times to form the three colored patterns of R, G and B is common to these processes. Therefore, the production cost is necessarily increased. There is also offered a problem that a yield is reduced as the number of processes increases. Further, in the electrodeposition process, formable patterns are limited. It is hence difficult to apply this process to an active matrix type (the so-called TFT type) color liquid crystal display device using TFT (thin film transistor) in the existing technique. Further, the printing process is poor in resolution and smoothness, and so fine-pitch patterns are difficult to form.
In order to cover up these faults, Japanese Patent Application Laid-Open No. 59-75205, 63-235901, 63-294503 or 1-217302 has proposed a process for producing a color filter using an ink-jet system. More specifically, it is described to provide a light-shielding film on a transparent substrate so as to have the prescribed regular apertures, and apply inks to the portions of the substrate corresponding to these apertures by the ink-jet system to form colored portions.
The production process for a color filter by the ink-jet system can reduce material cost because colored portions are formed only at necessary portions. In addition, the three colors can be applied at the same time, and so production process can be shortened, and the process is hard to be affected by dust. From such reasons that cost required for the production apparatus can be reduced, low material cost and high yield can be expected, so that it is possible to produce the color filter at lower cost compared with other production processes.
In the production apparatus of a color filter by the ink-jet system, a prescribed amount of each ink is applied at prescribed positions of a transparent substrate unlike the case of the general printer. Therefore, with respect to ink-droplet impact and color unevenness upon coloring, such a production apparatus is required to have precision higher by almost one order of magnitude than the case of the general printer.
Therefore, in the general printer of the ink-jet system, an ink is applied while conducting reciprocating scan of an ink-jet head, thereby making a record of an image, whereas the production apparatus of a color filter is so constructed that an ink-jet head is fixed to apply inks to a transparent substrate while scanning the transparent substrate in X-Y directions by reason of the precision required thereof. Such an apparatus is so constructed that the transparent substrate is sucked on a high-precision substrate chuck for the purpose of keeping a distance between the transparent substrate and the ink-jet head constant.
However, there has been a demand for development of an apparatus which can color a transparent substrate with still higher precision to prevent color unevenness.